Generally indicated above, the present invention is particularly directed toward security lock mechanisms of a type employed in custodial systems such as penitentiaries and for regulating access to secured areas such as military or industrial installations and other buildings where closely regulated access may be desirable, for example, hotels, etc.
In such applications, it is of course particularly important that the security lock mechanism be reliable and of relatively simple mechanical construction commensurate with the requirements of reliability as noted above and long-term operation.
The security lock mechanism of the present invention is also of a conventional type adapted for both deadlocked and slam-lock operation. Accordingly, it is initially necessary that the security lock mechanism be operable in a deadlocked position where the mechanism remains engaged until properly released, for example, by a remote control unit or by overriding means such as a key or electromechanical device functioning in response to a coded access card or the like.
After being opened by any of the means referred to above, it is then desirable that the security lock mechanism be of a type adapted for operation in a slam-lock mode. In such a mode, a locking bolt or the like is normally positioned in an extended position regulated by fettering means such as a double-acting spring so that as a door is slammed shut, the locking bolt will initially retract upon closing engagement of the door and then immediately extend in order to retain the door in closed engagement.
Obviously, the lock mechanism experiences substantial shock during slam-lock operation and it is particularly important to adapt the lock mechanism for reliable operation over extended periods with minimum failure or wear.
Numerous prior art lock mechanisms, adapted for operation in the manner generally referred to above, have been made available in substantial variety. For example, one such lock system is disclosed in U.S. Pat. No. 4,691,948 issued Sept. 8, 1987 to Austin, Jr., et al. That patent disclosed a fail-secure lock system using normally pneumatically actuated locking bolts which can be manually operated, for example, in the event of a power or air failure.
Many other examples of such lock systems have been made available and may be operable by cam mechanisms where a rotatable cam is coupled with a locking bolt, for example, by means of a rack and pinion coupling or other direct interconnection.
Generally, these prior art lock systems have been found to be satisfactory for their purposes. However, there has been found to remain a need for improved security lock mechanisms for use in applications such as those referred to above. In particular, there has been found to remain a need for improved security lock mechanisms capable of reliable operation over extended periods of time. It has further been found that such advantages can be best achieved where minimum mechanical shock is introduced or applied within the lock mechanism.